They both use the same SH-uX core which is Matsudaira's trademark.
The core materias used in various cartridges go under the radar - no one talks about them. I have a hunch from listening to many cartridges from the same manufacturer ( alnico, samarium cobalt, platinum etc ) with different core materials that we are listening to the core material as much as the cantilever/stylus/generator design.
I cant stand the platinum magnet Koetsu's. Don't know why - technically, but I've heard enough koetsu's of all types from the 80's onward black - rosewood - onyx golds to know there is a plasticky quality that pervades the platinum magnet Koetsu's compared to Suganos earlier cartridges. It has nothing to do with rolled off top end or lush midrange - there is a synthetic quality from mid to upper mid that grates - I'm thinking may be the magnets.
The only other platinum magnet cartridge I've heard is the VDH Colibri - and to me that sounds slightly coarse compared to his others, but not as bad as the Koetsu's.